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Peyer's patches (or aggregated lymphoid nodules) are organized lymphoid follicles, named after the 17th-century Swiss anatomist Johann Conrad Peyer. [1] They are an important part of gut associated lymphoid tissue usually found in humans in the lowest portion of the small intestine, mainly in the distal jejunum and the ileum, but also could be detected in the duodenum.
The mucosa-associated lymphoid tissue (MALT), also called mucosa-associated lymphatic tissue, is a diffuse system of small concentrations of lymphoid tissue found in various submucosal membrane sites of the body, such as the gastrointestinal tract, nasopharynx, thyroid, breast, lung, salivary glands, eye, and skin.
The Peyer's patch is an aggregate of lymphoid cells projected to the lumen of the gut which acts as a very important site for the initiation of the immune response. It forms a subepithelial dome where large number of B cell follicles with its germinal centers, T cell areas between them in a smaller number and dendritic cells are found.
Microfold cells (or M cells) are found in the gut-associated lymphoid tissue (GALT) of the Peyer's patches in the small intestine, and in the mucosa-associated lymphoid tissue (MALT) of other parts of the gastrointestinal tract.
The solitary lymphatic nodules are found scattered throughout the mucous membrane of the small intestine, but are most numerous in the lower part of the ileum.. Their free surfaces are covered with rudimentary villi, except at the summits, and each gland is surrounded by the openings of the intestinal glands.
The region of the lymph node called the paracortex immediately surrounds the medulla. Unlike the cortex, which has mostly immature T cells, or thymocytes, the paracortex has a mixture of immature and mature T cells. Lymphocytes enter the lymph nodes through specialised high endothelial venules found in the paracortex.
A 5,300-year-old antler shaped like an ice pick found in the melting ice. “Every perishable artifact was found amongst a backdrop of millions of obsidian” artifacts, the study said.
Germinal centers or germinal centres (GCs) are transiently formed structures within B cell zone (follicles) in secondary lymphoid organs – lymph nodes, ileal Peyer's patches, and the spleen [1] – where mature B cells are activated, proliferate, differentiate, and mutate their antibody genes (through somatic hypermutation aimed at achieving higher affinity) during a normal immune response ...